The overall objectives of this project are to validate the PROM IS pediatric item banks in 4 pediatric chronic illnesses, and to link pediatric and adult item banks. We developed 9 pediatric item banks during the first PROMIS grant cycle and have performed cross-sectional testing in children with several chronic illnesses. The proposed work is the natural next step toward integration of PROMIS scales into clinical research. We propose longitudinal studies in children with asthma, cancer, nephrotic syndrome, and sickle cell disease. Each study follows children through a clinical transition known to affect health-related quality of life, and each study will examine the responsiveness of the PROMIS instruments and estimate the minimum important difference (MID) for children. As part of these studies, we have proposed to test a new method for establishing MID and to compare that method with traditional distributional and anchor-based methods. The second overall objective is to link PROMIS pediatric item banks with PROMIS adult item banks. We designed most of the pediatric banks to measure the same underlying trait as their counterpart adult banks (e.g., fatigue), but used the concepts and language of children. We will administer pediatric and adult short forms to adolescents with chronic illnesses with a cross-sectional data collection. For this objective, we will use factor analysis and structural equation modeling to establish the empirical relationships between the pediatric and adult item banks and domains, and, to the extent supported by those relationships, use item response theory to link the pediatric and adult item banks. This study will enable researchers to have comparable scores between children and adults participating in the same study and enable longitudinal studies that follow children into adulthood.